This invention relates to a method and apparatus for precisely separating non-metallic materials into a plurality of smaller pieces, and more particularly, this the invention relates to a method and apparatus for splitting non-metallic materials by controlling internal forces and propagating a microcrack to separate a material along a desired path.
Propagating a microcrack in a brittle material by using a laser has been known for at least three decades by those skilled in the art. In U.S. Pat. No. 3,610,871 to Lumley, the disclosure which is hereby incorporated by reference in its entirety, ceramic substrates are parted by reflecting a focused laser beam off a mirrored surface so that the focal point of the beam impinges upon the lower surface of the substrate of an extreme edge. After a localized fracture, the substrate is displaced, relative to the laser beam, to intercept the beam before it is reflected from the mirrored surface. The laser beam is intercepted by the upper surface of the substrate before the beam reaches its focal point, resulting in the beam energy being distributed over a larger area. As displacement continues, the localized fracture is controllably propagated.
This technique has not yet become commercially viable for many applications because of slow process speeds, complicated laser modes, poor understanding of laser scribing mechanisms, and time consuming, archaic two-step processes (e.g. scribe and break), which generate particulate and microcracks, thus counteracting a primary advantage of laser separation.
To overcome these and other known disadvantages, fast, reliable laser scribing, single step separation, and efficient use of a device that is simple yet powerful are desirable.
It is therefore an object of the present invention to provide a method and apparatus that separates non-metallic materials through highly controlled propagation of a microcrack and precise splitting.
The present invention is advantageous and includes features that enable fast process speeds, full separation, increased accuracy, highly controlled thermal gradients, improved edge quality, effective crosscutting, reduced edge effects, a simplified design, and increased flexibility and reduced cost.
The present invention is advantageous and provides a method and apparatus for splitting non-metallic substrates such as silicon or ceramic as non-limiting example, and comprises the steps of initiating a microcrack within a substrate and scribing the substrate with a laser beam at a heat affected zone that has been imparted onto the substrate by the laser beam. The microcrack is quenched at a quenching region that is contained within the heat affected zone by passing fluid from a quenching nozzle onto the substrate. A force is applied onto the substrate at a location behind the quenching region to break the substrate while maintaining residual forces below a critical breaking force in front of the quenching region.
The microcrack can be initiated with a mechanical initiator. In one aspect of the present invention, the laser beam is directed around the quenching nozzle via mirrors associated with the quenching nozzle. The fluid that is passed from the quenching nozzle can be a liquid and/or gas. A vacuum can also be drawn through the nozzle to remove any residual liquid and control gas flow. The temperature of the substrate can be elevated in a programmed manner before scribing, such as passing laser light through one of either a faceted or difractive optical lens element.
In yet another aspect of the present invention, the substrate is scribed with a laser beam via an integrated cracking device. The quenching nozzle is integral with the integrated cracking device. In yet another aspect of the present invention, the integrated cracking device includes a housing with the quenching nozzle mounted on the housing. Optics are fitted within the housing for receiving and directing the laser beam onto the substrate. In one aspect of the present invention, the optics include a mirror and single element lens fitted within the housing. The single element lens can comprise a double asymmetric cylinder lens element.